There must be stock somewhere in the world of wave 3 Deluxes, because they didn't really show up much anywhere. Maybe they might get dumped here cheap for a BigW sale later this year. At least, it might be something some of us will have to hope for if we don't want to pay secondary market prices.
(we never got Siege Apeface here, despite all those 2019 Siege Megatrons & Thundercrackers before Christmas 2020... so you just never know what we will get and what we will miss)

As dirge noted, the US exclusives coming here is dictated by Hasbro America.
And missing waves of regular lines here can just come down to not needing a restock before the cut-off in China of that wave (some waves can end up only being a couple months apart)... like if not enough retailers are interested in a particular size class (like the Battlemasters) to need more imported into the country as often, or if we were allocated too much stock of an earlier wave by Hasbro America.